I have got a Robox agility dvr recorder 500gb with only 2 cameras attached, the problem is over the last 2 nights the motion detector is saying it has picked something up about 3 times a minute , it only happens when its dark..I know this happens when it rains but this is when it is dry..I have looked through the recordings and cant find anything that may trigger it and it is only happening on one camera,I have put the manual away that good I cant now find it